What does this "Recover" command, "Build Surface/Sector" do and how do I use it? (alt-b)

It's been a while so, I'm a bit fuzzy on how it works. But...

Select 3 vertices and use the Build Surface command. It'll make a triangle surface there. Make sure you check it because sometimes it builds it inverted and you have have to scale it by -1 to fix it.

TIP:
Generally speaking, there is no reason to ever delete a surface. It is almost always preferable to set +GEO = 0 instead.

Deleting surfaces is useful when hacking up 3d0s.

I was wondering what it was for because I had two separate surfaces and I needed to make a sector between them. The build thing says "sector" as well but I could never get it to do that -- and it will only build a surface with exactly 3 vertexes selected. I eventually was able to do it by hand, but meh, what a pain.

I always thought it did something like that but never got it to work. Thanks, Alco. Might be useful for when JED decides to delete surfaces on its own.